When filling the fuel tank of a motor vehicle, it is a common measure to recover the vapor escaping the tank when filling it with liquid fuel. This measure is taken for both safety and environmental reasons. The vapor recovery is achieved, for instance, by arranging a vapor suction nozzle next to the fuel dispensing nozzle of a pistol grip for filling the tank with fuel. Vapor is then removed from the tank during filling, at a certain rate, which is often controlled by the standard rate of at which fuel is dispensed to the tank. Vapor recovery systems typically comprise a pump for feeding vapor, from the tank of the vehicle, to the fuel container from which fuel is fed to the vehicle. This mutual exchange of vapor/fuel is continuously performed when filling a vehicle with fuel.
However, today some vehicles are fitted with an on-board refueling vapor recovery (ORVR) system which vents the head space in the vehicle tank through a charcoal-filter, so that the vapor is absorbed by the charcoal.
A fuel dispensing unit fitted with a vapor recovery system but not able to detect vehicles equipped with ORVR systems, will waste energy and will ingest excessive air into the fuel container.
Today several techniques exist for detecting if a vehicle is equipped with an ORVR system.
U.S. Pat. No. 5,956,259, for example, discloses a fuel dispenser system configured to receive a signal from a vehicle transponder indicative of the presence of an ORVR system on the vehicle. If an ORVR equipped vehicle is detected, the fuel dispenser system deactivates its vapor recovery system.
WO 00/50850 discloses a fuel dispensing unit incorporating a vapor recovery system having a density detector for identifying the vapor composition of recovered vapor, and if the vapor is identified as substantially non-hydrocarbon (ORVR equipped vehicle) the operational rate of vapor collection is controlled accordingly.
A problem with existing fuel dispensers capable of detecting ORVR equipped vehicles is that they are relatively complicated and expensive both in respect of construction and production.